Christopher also looked back with gratitude on how far he had come from a childhood in Scranton, N.D., marked by bitter winters and modest circumstances. His father was a bank cashier who fell ill, and the family moved to Southern California during the Depression. After his father's death his mother supported the family of five children as a sales clerk.
An ensign in the U.S. Navy reserves, he was called up to active duty during World War II and served in the Pacific.
He received his undergraduate degree from the University of Southern California in 1945 and, after attending Stanford Law School, served as a clerk to Supreme Court Justice William O. Douglas in 1949 and 1950.
In the late 1960s, he was a deputy attorney general in the administration of Lyndon Johnson.
In 2008, Christopher was co-chairman of a bipartisan panel that studied the recurring question of who under U.S. law should decide when the country goes to war. It proposed that the president be required to inform Congress of any plans to engage in "significant armed conflict" lasting longer than a week.
As a successful Los Angeles lawyer, Christopher had a seven-figure income, and a beach house in fashionable Santa Barbara.
He is survived by his wife Marie, and had four children in two marriages: Lynn, Scott, Thomas, and Kristen. Plans were pending for a private memorial service.
AP writer Andrew Dalton contributed to this report from Los Angeles. Barry Schweid reported from Washington.